Oil separator unit

ABSTRACT

An oil separator unit including an upstream member having an opening through which the blowby gas passes, a downstream member having a hit portion hit by the blowby gas, and a porous member trapping the oil mist contained in the blowby gas that has passed through the through hole. The upstream member includes an upstream surface facing a first surface of the porous member and a pair of recesses formed in substantially U-shapes along circumference portions in both end sides on an upstream surface of the upstream member, and the downstream member includes a pair of flange parts formed in substantially U-shapes so as to fit in the pair of recesses.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2018-157527 filed on Aug. 24, 2018, thecontent of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to an oil separator unit configured to separateoil mist contained in blowby gas.

DESCRIPTION OF THE RELATED ART

There have been known so-called impactor filter-type oil separatorunits, which include an upstream plate with multiple through holesthrough which blowby gas passes, a downstream plate that is hit by theblowby gas that has passed through the through holes, and a fibermaterial disposed between the pair of plates such that there is a gapbetween the fiber material and the surface of the upstream plate. Suchan oil separator unit is described in, for example, Specification ofUnited States Patent Application Publication No. 2011/0179755(US2011/0179755A). In a unit described in US2011/0179755A, a pair ofplates and a fiber material are formed in approximately rectangularshapes elongated in the up-down direction, the pair of plates arecoupled through a pair of upper and lower connecting parts, and theposition in the up-down direction of the fiber material is regulated bythe pair of upper and lower connecting parts.

However, in the case of the unit that regulates the position in theup-down direction of the fiber material using the pair of upper andlower connecting parts, such as US2011/0179755A, it is difficult todispose the pair of plates at high positional accuracy. Therefore, it isdifficult to sufficiently separate oil mist.

SUMMARY OF THE INVENTION

An aspect of the present invention is an oil separator unit configuredto separate an oil mist contained in a blowby gas generated in aninternal combustion engine. The oil separator unit includes: an upstreammember disposed on an upstream side in a flow direction of the blowbygas and having an opening through which the blowby gas passes; adownstream member disposed on a downstream side in the flow direction ofthe blowby gas and having a hit portion hit by the blowby gas; and aporous member including a first surface facing the upstream member and asecond surface facing the downstream member and formed in asubstantially rectangular shape with a predetermined thickness so as totrap the oil mist contained in the blowby gas that has passed throughthe through hole. The upstream member includes an upstream surfacefacing the first surface, and a pair of recesses formed in substantiallyU-shapes along circumference portions in both end sides on the upstreamsurface. The downstream member includes a pair of flange parts formed insubstantially U-shapes so as to fit in the pair of recesses.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features, and advantages of the present invention willbecome clearer from the following description of embodiments in relationto the attached drawings, in which:

FIG. 1 is a diagram showing schematically a configuration of an oilseparator system incorporating an oil mist separator according to anembodiment of the invention;

FIG. 2 is an exploded perspective view of the oil mist separatoraccording to the embodiment of the present invention;

FIG. 3 is a simplified sectional view showing a major part of theassembled configuration of the oil mist separator according to theembodiment of the present invention;

FIG. 4A is an exploded perspective view of the oil separator unitaccording to the embodiment of the present invention, seen from arear-left side;

FIG. 4B is an exploded perspective view of the oil separator unitaccording to the embodiment of the present invention, seen from afront-left side;

FIG. 5 is a perspective view showing the assembled configuration of theoil separator unit according to the embodiment of the present invention;

FIG. 6 is a front view of an upstream plate constituting the oilseparator unit according to the embodiment of the present invention;

FIG. 7 is a front view of a downstream plate constituting the oilseparator unit according to the embodiment of the present invention;

FIG. 8 is a side view showing the assembled configuration of the oilseparator unit according to the embodiment of the present invention;

FIG. 9A is a front view of an oil separator unit according to amodification of the embodiment; and

FIG. 9B is a sectional view taken along line B-B of FIG. 9A.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment of the present invention will be describedwith reference to FIGS. 1 to 9B. An oil separator unit according to anembodiment of the present invention configures a part of an oil mistseparator. FIG. 1 is a drawing showing a schematic configuration of anoil separator system including the oil mist separator according to thepresent embodiment and schematically shows an upper portion of an engine1 as an internal combustion engine. In FIG. 1, the front-rear directionand up-down direction of a vehicle having the engine 1 mounted thereonare shown by arrows. The front-rear direction corresponds to the vehiclelength direction, and the up-down direction corresponds to the vehicleheight direction (gravity direction).

As shown in FIG. 1, the engine 1 is a V-type engine (e.g., V-6 engine),in which multiple cylinders are disposed in a V-shape in a side view.Specifically, the engine 1 is formed as a V-type engine in which a pairof front and rear head portions 3F and 3R are disposed on a cylinderblock 2 so as to be inclined forward and rearward, respectively, withrespect to a vertical line and thus form a pair of front and rear banks4F and 4R.

The head portions 3F and 3R each include a cylinder head mounted on theupper end of the cylinder block 2, a cylinder head cover mounted on theupper end of the cylinder head, and the like. A crankcase 5 is disposedunder the cylinder block 2, and an oil pan is disposed under thecrankcase 5. Lubricating oil is stored into the oil pan through a crankchamber 5 a in the crankcase 5.

FIG. 1 shows the configuration of the intake system of the engine 1.This intake system includes an air cleaner 6, an intake passage 7, andan intake manifold 8 and is configured to supply intake air to thecombustion chambers of the cylinders of the engine 1. A compressor 9 bforming a turbocharger 9 with a turbine 9 a is disposed on the intakepassage 7, and a throttle valve 10 that controls the amount of intakeair supplied to the engine 1 is disposed downstream of the compressor 9b. In a state in which the engine rotational speed is low (duringnon-turbocharging), the pressure in the intake manifold 8 becomesnegative, and intake air is supplied to the engine 1. On the other hand,in a state in which the engine rotational speed is high (duringturbocharging), intake air is compressed by the turbocharger 9 and thusthe pressure in the intake manifold 8 becomes positive.

The oil separator system 100 according to the present embodimentincludes a pair of oil mist separators 101 (101F, 101R) mounted on theupper ends of the pair of front and rear head portions 3F and 3R, apassage 11 connecting the front oil mist separator 101F and the intakemanifold 8, and a passage 12 branched from the intake passage 7 betweenthe air cleaner 6 and compressor 9 b and connected to the rear oil mistseparator 101R. An open/close valve 13 is disposed on one end of thepassage 11, that is, the oil mist separator 101F-side end thereof. Theopen/close valve 13 is configured to be opened when the pressure in theintake manifold 8 is negative and to be closed when the pressure ispositive. The open/close valve 13 is also configured to, when opened,permit the gas flow from the oil mist separator 101F to the passage 11and prohibit the flow in the opposite direction.

The crank chamber 5 a communicates with the internal spaces SP (FIG. 3)of the oil mist separators 101F and 101R through communication holes(not shown) provided in the cylinder block 2 and cylinder heads. Blowbygas containing unburned components is leaked from the combustionchambers of the cylinders of the engine 1 into the crank chamber 5 aduring operation of the engine. Oil mist floating in the crank chamber 5a is mixed into the blowby gas. In FIG. 1, for convenience, the blowbygas containing unburned components is represented by arrows A1 and B1,and the blowby gas containing the oil mist is represented by arrows A2and B2.

When the pressure in the intake manifold 8 is negative, the open/closevalve 13 is opened, and the blowby gas is sucked into the intakemanifold 8 through the front oil mist separator 101F, open/close valve13, and passage 11, as shown by arrows A1, A2, and A3 (solid lines) inFIG. 1. In this process, the oil mist contained in the blowby gas isseparated and removed by the oil mist separator 101F, and the blowby gasnot containing the oil mist is supplied to the intake manifold 8. Atthis time, as shown by an arrow A4 (solid line), fresh air is suppliedinto the crank chamber 5 a through the passage 12 and the internal spaceof the rear oil mist separators 101R and thus the crank chamber 5 a isventilated.

On the other hand, when the pressure in the intake manifold 8 ispositive, the open/close valve 13 is closed, and the blowby gas issucked into the intake passage 7 from upstream side of the compressor 9b through the oil mist separator 101R and passage 12, as shown by arrowsB1, B2, and B3 (dotted lines) in FIG. 1. In this process, the oil mistcontained in the blowby gas is separated and removed by the oil mistseparators 101R. Then, the blowby gas not containing the oil mist issupplied to the intake manifold 8 through the compressor 9 b andthrottle valve 10.

The configuration of the oil mist separators 101 (101F, 101R) will bedescribed. The front oil mist separator 101F and rear oil mist separator101R have the same basic configuration. FIG. 2 is an explodedperspective view of an oil mist separator 101 (a perspective view seenfrom a front-lower side). FIG. 3 is a simplified sectional view showinga major part configuration of the assembled oil mist separator 101. Asin FIG. 1, in FIGS. 2 and 3, the front-rear direction and up-downdirection are represented by arrows. In FIG. 2, the left-right directionis also represented by arrows. The left-right direction corresponds tothe vehicle width direction. In FIG. 3, a part of a cylinder head 16 isshown.

Since the engine 1 is a V-type engine, the upper surface of the cylinderhead having the oil mist separator 101 mounted thereon is inclined inthe front-rear direction with respect to a horizontal plane. For thisreason, a direction perpendicular to the upper surface (inclinedsurface) of the cylinder head is not the up-down direction in an exactsense, but an approximate up-down direction. However, although it ismounted on the inclined surface, the oil mist separator 101 sufficientlyworks and therefore the direction perpendicular to the upper surface ofthe cylinder head is handled as the up-down direction (gravitydirection) below. That is, not only the direction in which the oil dropsbut also the direction in which the oil flows along the wall surface ofa plate part 51 (FIG. 4A) (to be discussed later) due to the gravity ishandled as the gravity direction.

As shown in FIGS. 2 and 3, the oil mist separator 101 includes a lowercase 20 mounted on the upper surface of the cylinder head 16 with agasket 15 therebetween, an upper case 30 fixed to the upper surface ofthe lower case 20, and an oil separator unit (simply referred to as the“separator unit”) 102 contained in a space formed by the cases 20 and30. The lower case 20 and upper case 30 form a part of a cylinder headcover. These cases also form a part of the head portion 3F or 3R in FIG.1 with a cylinder head 16. The lower case 20 is formed in anapproximately tabular shape on the whole. The upper case 30 is formed ina housing shape having an open at its bottom on the whole, and thebottom is covered by the case 20.

The lower case 20 and upper case 30 are formed by molding resin. Aflange 21 is disposed over the entire periphery of the lower case 20. Aflange 31 is disposed over the entire periphery of the lower end of theupper case 30 so as to correspond to the flange 21. The lower case 20and upper case 30 are integrated with each other, for example, byvibration welding the upper surface of the flange 21 and the lowersurface of the flange 31 and thus form a space SP therein. The lowercase 20 and upper case 30 may be integrated with each other using adifferent technique.

A partition 32 extends in the left-right direction in the upper case 30,and the space SP is partitioned into a rear first space SP1 and a frontsecond space SP2 by the partition 32. An approximately U-shaped notch 33is formed in the partition 32 upward from the bottom surface thereof soas to correspond to the shape of the periphery of the separator unit102. A recessed slit 33 a is disposed over the entire periphery of thenotch 33, and the periphery of the separator unit 102 is fitted to theslit 33 a from below, as described later. In this state, the cases 20and 30 are welded together. Thus, the separator unit 102 is sandwichedbetween the cases 20 and 30 with the position thereof regulated by theslit 33 a. In this way, the oil mist separator 101 is assembled. Theassembled oil mist separator 101 is fixed to the upper surface of thecylinder head 16 using multiple bolts that penetrate the flanges 21 and31.

A through hole 22 formed in an approximately rectangular shape in a planview is provided in the left end of the lower case 20 so as to penetratethe lower case 20 in the up-down direction. The first space SP1 and thecrank chamber 5 a under the cylinder block 2 communicate with each otherthrough the through hole 22. Thus, the blowby gas can be caused to flowfrom the crank chamber 5 a into the first space SP1 through the throughhole 22. The blowby gas, which has flown into the first space SP1, flowsinto the second space SP2 while the oil mist is separated therefrom bythe separator unit 102. An approximately cylindrical pipe 34 isprotruded forward from the upper end of the upper case 30. Through thepipe 34, the second space SP2 and passage 12 (FIG. 1) or open/closevalve 13 (FIG. 1) communicate with each other. Thus, the blowby gas canbe caused to flow out of the second space SP2 through the pipe 34.

The lower case 20 is provided with a swelling portion 23 that swellsdownward. As shown in FIG. 3, the swelling portion 23 is locateddirectly in front of the notch 33 and forms a recessed space SP3 underthe second space SP2. A small-diameter through hole 24 is provided inthe lowest portion of the swelling portion 23 so as to penetrate thelower case 20 in the up-down direction. The second space SP2 and crankchamber 5 a communicate with each other through the through hole 24.Thus, the oil separated by the separator unit 102 is guided to the spaceSP3 and then returned to the crank chamber 5 a through the through hole24.

The configuration of the separator unit 102 according to the presentembodiment will be described in detail below. FIGS. 4A and 4B areexploded perspective views of the separator unit 102 seen from arear-left side and a front-left side). FIG. 5 is a perspective viewshowing the assembled separator unit 102 (seen from a rear-left side).For convenience, in these drawings, the up-down direction, front-reardirection, and left-right direction are defined as in FIGS. 1 to 3, andthe configurations of the separator unit 102 will be described inaccordance with this definition. The separator unit 102 is a smallassembly having an overall length of several centimeters order in theup-down direction and is assembled without using fastening members, suchas a bolt. Hereafter, the up-down direction, front-rear direction, andleft-right direction may be referred to as the height direction,thickness direction, and width direction, respectively. The separatorunit 102 is formed in the height direction, thickness direction, andwidth direction.

The separator unit 102 is formed as an impactor filter type. As shown inFIGS. 4A and 4B, the separator unit 102 includes an upstream plate 40disposed on the upstream side, that is, on the rear side of the flowdirection of the blowby gas, a downstream plate 50 disposed on thedownstream side, that is, on the front side of the flow direction of theblowby gas, and a fiber member 60 disposed between the upstream plate 40and downstream plate 50.

The fiber member 60 has a front surface 61 and a rear surface 62, anupper surface 63 and a lower surface 64, and a left surface 65 and aright surface 66. The fiber member 60 is formed in an approximatelyrectangular parallelepiped shape on the whole. The length in the up-downdirection (longitudinal direction) of the fiber member 60 is longer thanthe length in the left-right direction (lateral direction) (width)thereof. That is, the fiber member 60 is formed so as to be elongated inthe up-down direction. The rear surface 62 of the fiber member 60 isopposed to the upstream plate 40, and the front surface 61 thereof isopposed to the downstream plate 50.

The upstream plate 40 includes an approximately rectangular plate part41 having a predetermined thickness in the front-rear direction andmultiple (10 in the drawings) spacers 42 protruded forward from thefront surface 41 a of the plate part 41. As shown in FIG. 4A, the rearsurface 41 b of the plate part 41 is formed so as to be flat orapproximately flat. The upstream plate 40 is integrally molded fromresin. Also, the upstream plate 40 is formed so as to be bilaterallysymmetrical on the whole. FIG. 6 is a front view of the upstream plate40. In FIG. 6, the position of the fiber member 60 when the separatorunit 102 is assembled is shown by a chain double-dashed line.

As shown in FIGS. 4A and 6, the length in the up-down direction(longitudinal direction) of the plate part 41 is longer than the lengthin the left-right direction (lateral direction) (width) thereof. Thatis, the plate part 41 has a constant or approximately constant width inthe left-right direction and is formed so as to be elongated in theup-down direction. In the central portion in the left-right direction ofthe plate part 41, a through hole 43 elongated in the up-down directionwith a constant width is formed. The upper and lower ends of the throughhole 43 are formed in arc shapes (semicircular shapes).

As shown in FIGS. 4B and 6, the spacers 42 are disposed so as to beequally spaced in the up-down direction from the upper end to the lowerend of the through hole 43 and to be bilaterally symmetrical withrespect to the through hole 43. The spacers 42 are formed in tabularshapes and extend in parallel with each other in the left-rightdirection. For convenience, the spacers 42 (421 to 425) may be referredto as first spacers 421, second spacers 422, third spacers 423, fourthspacers 424, and fifth spacers 425 in the top-to-bottom order.

The front surfaces 42 a of the left and right spacers 421 to 425configure support surfaces that support the fiber member 60 bycontacting the rear surface 62 of the fiber member 60. The protrudinglengths of the spacers 421 to 425, that is, the lengths from the frontsurface 41 a of the plate part 41 to the front surfaces 42 a of thespacers 421 to 425 are equal to each other. The front surfaces 42 a ofthe spacers 421 to 425 are located on the same virtual plane extendingin the up-down and left-right directions.

Cylindrical protrusions 42 b having the same height (length) areprotruded from the central portions in the left-right direction of thefront surfaces 42 a of the left and right spacers 421 to 425. The innerend surfaces in the left-right direction of the spacers 421 to 425 arelocated on planes extending from the opening end surfaces (left andright end surfaces) of the through hole 43. Accordingly, the left endsurfaces of the right spacers 421 to 425 are located on the same plane,and the right end surface of the left spacers 421 to 425 are located onthe same plane. For this reason, the lengths in the left-right directionof the front surfaces 42 a of the spacers 421 to 425 are equal to eachother.

Guides 44 protruding forward than the front surfaces 42 a of the spacers42 are connected to the outside surfaces in the left-right direction ofthe left and right first, third, and fifth spacers 421, 423, and 425 ofthe spacers 421 to 425. The protruding lengths of the guides 44 arelonger than the protruding lengths of the protrusions 42 b, as shown inFIG. 4B, and shorter than the thickness (the length in the front-reardirection) of the fiber member 60, as shown in FIG. 5. For example, theprotruding lengths of the guides 44 are set within a range that is ½ to⅔ of the thickness of the fiber member 60.

As shown in FIG. 6, the right end surfaces 44 a of the guides 44 of theleft first, third, and fifth spacers 421, 423, and 425 are located onthe same plane, and the left end surfaces 44 b of the guides 44 of theright first, third, and fifth spacers 421, 423, and 425 are also locatedon the same plane. The lengths from the right end surfaces 44 a to theleft end surfaces 44 b of the guides 44 are equal to the width (thelength in the left-right direction) of the fiber member 60. For thisreason, the right end surfaces 44 a configure support surfaces thatsupport the left surface 65 of the fiber member 60 by contacting theleft surface 65, and the left end surfaces 44 b configure supportsurfaces that support the right surface 66 of the fiber member 60 bycontacting the right surface 66.

A plate-shaped guide 45 is protruded forward from the front surface 41 aof the plate part 41 below the through hole 43. The protruding length(the length in the front-rear direction) of the guide 45 is equal to thelengths from the front surface 41 a of the plate part 41 to the frontend surfaces of the guides 44. The upper surface 45 a of the guide 45configures a support surface that supports the lower surface 64 of thefiber member 60 by contacting the lower surface 64.

A pair of upper and lower recesses (concave portions) 46 and 47 having apredetermined depth are provided in the front surface 41 a of the platepart 41. The upper recess 46 is formed in an approximate U-shape alongthe outside shape of the plate part 41 so as to extend from the upperend of the front surface 41 a of the plate part 41 through the left andright outer sides of the left and right first spacers 421 to the leftand right outer sides of the left and right second spacers 422. Thelower recess 47 is formed in an approximate U-shape along the outsideshape of the plate part 41 so as to extend from the lower end of thefront surface 41 a of the plate part 41 through the left and right outersides of the left and right fifth spacers 425 to the left and rightouter sides of the left and right fourth spacers 424. The bottomsurfaces 46 a and 47 a of the recesses 46 and 47 are formed on the samevirtual plane extending in the up-down and left-right directions. Asshown in FIG. 4B, the area between the left and right lower ends of therecess 46 and the left and right upper ends of the recess 47 isprotruded forward than the recesses 46 and 47. This area may be referredto as a protrusion (convex portion) 48.

As shown in FIGS. 4B and 6, engagement portions are partially disposedon the approximately U-shaped peripheral surface (side surface) of therecess 46, that is, on a boundary surface 46 b between the bottomsurface 46 a of the recess 46 and the front surface 41 a along thebottom surface 46 a. More specifically, an engagement recess (concaveportion) 461 that is approximately rectangularly recessed from a leftboundary surface 46 b is disposed adjacent to the left end surface ofthe left second spacer 422, an engagement recess (concave portion) 462that is approximately rectangularly recessed from a right boundarysurface 46 b is disposed adjacent to the right end surface of the rightsecond spacer 422, and an engagement recess (concave portion) 463 thatis approximately rectangularly recessed from an upper boundary surface46 b is disposed above the through hole 43. The left end surface of theguide 44 of the left first spacer 421 and the right end surface of theguide 44 of the right first spacer 421 are located on the same orapproximately the same planes as the boundary surfaces 46 b.

Engagement portions are partially disposed on the approximately U-shapedperipheral surface (side surface) of the recess 47, that is, on aboundary surface 47 b between the bottom surface 47 a of the recess 47and the front surface 41 a along the bottom surface 47 a. Morespecifically, an engagement recess (concave portion) 471 that isapproximately rectangularly recessed from a left boundary surface 47 bis disposed adjacent to the left end surface of the left fourth spacer424, an engagement recess (concave portion) 472 that is approximatelyrectangularly recessed from a right boundary surface 47 b is disposedadjacent to the right end surface of the right fourth spacer 424, and anengagement protrusion (convex portion) 473 that is approximatelyrectangularly protruded from a lower boundary surface 47 b is disposedadjacent to the lower surface of the guide 45 below the through hole 43.The left end surface of the guide 44 of the left fifth spacer 425 andthe right end surface of the guide 44 of the right fifth spacer 425 arelocated on the same or approximately the same planes as the boundarysurfaces 47 b.

As shown in FIGS. 4A and 4B, the downstream plate 50 includes theapproximately rectangular plate part 51 having a predetermined thicknessin the front-rear direction, a pair of upper and lower flanges 52 and 53disposed behind the plate part 51, and multiple connecting parts 54 thatcouple the plate part 51 and flanges 52 and 53. As shown in FIG. 4B, thefront surface 51 a of the plate part 51 is formed so as to be flat orapproximately flat. The downstream plate 50 is integrally molded fromresin. Also, the downstream plate 50 is formed so as to be bilaterallysymmetrical on the whole. FIG. 7 is a rear view of the downstream plate50. In FIG. 7, the position of the fiber member 60 when the separatorunit 102 is assembled is shown by a chain double-dashed line.

As shown in FIGS. 4A and 7, the length in the up-down direction(longitudinal direction) of the plate part 51 is longer than the lengthin the left-right direction (lateral direction) (width) thereof. Thatis, the plate part 51 has a constant or approximately constant width inthe left-right direction and is formed so as to be elongated in theup-down direction. More specifically, the shape of the plate part 51approximately matches the shape of the front surface 41 a of the platepart 41) of the upstream plate 40, that is, the shape of the frontsurface 41 a except for the recesses 46 and 47. The plate part 51configures a hit portion that is hit by the blowby gas that has passedthrough the through hole 43 of the upstream plate 40 and the fibermember 60.

Multiple (3 in the drawings) columnar ribs 55 having approximatelyrectangular cross-sections protrude rearward from the rear surface 51 bof the plate part 51 so as to be equally spaced in the left-rightdirection. For convenience, the ribs 55 (551 to 553) may be referred toas the first rib 551, second rib 552, and third rib 553 in theleft-to-right order. The ribs 551 to 553 are extended in parallel witheach other in the up-down direction, and the extending direction thereofis perpendicular to the extending direction (left-right direction) ofthe spacers 421 to 425 (FIG. 6). The lengths (widths) in the left-rightdirection of the ribs 551 to 553 are equal to each other.

The second rib 552 is located in the front of the through hole 43 and onthe central portion in the left-right direction of the plate part 51. Inthe assembled separator unit 102, the first rib 551 is locatedapproximately in the same position in the left-right direction as theline of the protrusions 42 b (FIG. 6) provided at the left spacers 421to 425 of the upstream plate 40, and the third rib 553 is locatedapproximately in the same position in the left-right direction as theline of the protrusions 42 b provided at the right spacers 421 to 425 ofthe upstream plate 40. In other words, the second rib 552 is disposed soas to correspond to the position of the through hole 43, the first rib551 is disposed so as to correspond to the positions of the left spacers421 to 425, and the third rib 553 is disposed so as to correspond to thepositions of the right spacers 421 to 425.

The rear surfaces 55 a of the ribs 551 to 553 configure support surfacesthat support the fiber member 60 by contacting the front surface 61 ofthe fiber member 60.

The protruding lengths of the ribs 551 to 553, that is, the lengths fromthe rear surface 51 b of the plate part 51 to the rear surfaces 55 a ofthe ribs 551 to 553 are equal to each other. The rear surfaces 55 a ofthe ribs 551 to 553 are located on the same virtual plane extending inthe up-down and left-right directions. The protruding lengths of theribs 551 to 553 are shorter than the protruding lengths of the spacers421 to 425.

Multiple (five) cylindrical protrusions 55 b having the same heights aredisposed in equally spaced positions in the up-down direction on each ofthe rear surfaces 55 a of the first rib 551 and third rib 553. Theprotrusions 55 b are formed in the same shape as the protrusions 42 b ofthe spacer 42 of the upstream plate 40. Also, in the assembled separatorunit 102, the protrusions 55 b are disposed in the same positions in theup-down and left-right directions as the protrusions 42 b.

The upper flange 52 is formed in an approximate U-shape, and the innerperipheral surface 52 a thereof is approximately the same as the shapeof the outer peripheral surface 51 c (edge) of the plate part 51. Theouter peripheral surface 52 b thereof is approximately the same as theshape of the outer peripheral surface 41 c (FIG. 4A) of the plate part41 of the upstream plate 40. The lower flange 53 is formed in anapproximate U-shape, and the inner peripheral surface 53 a thereof isapproximately the same as the shape of the outer peripheral surface 51 cof the plate part 51. The outer peripheral surface 53 b thereof isapproximately the same as the shape of the outer peripheral surface 41 cof the plate part 41 of the upstream plate 40. The rear surfaces 52 cand 53 c of the flanges 52 and 53 are formed so as to be flat and arelocated on the same virtual plane extending in the up-down andleft-right directions. The lengths (thicknesses) in the front-reardirection of the flanges 52 and 53 are approximately equal to the depthsof the recesses 46 and 47 (FIG. 4B) of the upstream plate 40.

The connecting parts 54 are formed in tabular shapes havingapproximately rectangular cross-sections. As shown in FIG. 7, theconnecting parts 54 include connecting parts 541 to 543 having one ends(rear ends) fixed to the left and right lower ends and upper end of theinner peripheral surface 52 a of the flange 52. The connecting parts 541to 543 are extended in the front-rear direction, and the other ends(front ends) thereof are fixed to the left and right lower ends andupper end of the plate part 51. Thus, both ends and central portion inthe longitudinal direction of the flange 52 extending in an approximateU-shape are supported by the connecting parts 541 to 543. The connectingparts 541 to 543 have convex cross-sectional shapes corresponding to theshapes of the engagement recesses 461 to 463 (FIG. 6) of the plate part41 of the upstream plate 40. Thus, when the separator unit 102 isassembled as shown in FIG. 5, the flange 52 is fitted to the recess 46,and the connecting parts 541 to 543 are fitted to the engagementrecesses 461 to 463.

In this fitted state, the right end surface 541 a of the connecting part541 and the left end surface 542 a of the connecting part 542 shown inFIG. 7 are located on the same or approximately the same planes as theright end surface 44 a of the left guide 44 and the left end surface 44b of the right guide 44 of the upstream plate 40 shown in FIG. 6. Thus,as with the end surfaces 44 a and 44 b of the guides 44, the endsurfaces 541 a and 542 a 6 configure support surfaces that support theleft surface 65 and right surface 66 of the fiber member 60. That is,the connecting parts 541 and 542 are located in the same position in theup-down direction as the second spacers 422 of the upstream plate 40 andoutside the second spacers 422 in the left-right direction, as well asserve as support portions that support the fiber member 60, as with theguides 44. The lower surface 543 a of the connecting part (centralconnecting part) 543 configures a support surface that supports theupper surface 63 of the fiber member 60.

Also, as shown in FIG. 7, the connecting parts 54 include connectingparts 544 to 547 having one ends (rear ends) fixed to the left and rightupper ends and left and right lower ends and of the inner peripheralsurface 53 a of the flange 53. The connecting parts 544 to 547 extend inthe front-rear direction. The other ends (front ends) of the connectingparts 544 and 545 are fixed to the left and right ends of the plate part51, and the other ends of the connecting parts 546 and 547 are fixed tothe left and right lower ends of the plate part 51. Thus, both ends andthe central portion in the longitudinal direction of the flange 53extending in an approximate U-shape are supported by the connectingparts 544 to 547.

The connecting parts 544 and 545 have convex cross-sectional shapescorresponding to the shapes of the engagement recesses 471 and 472 (FIG.6) of the plate part 41 of the upstream plate 40. The lengths in theup-down direction of the connecting parts 546 and 547 are equal to thelength in the up-down direction of the engagement protrusion 473, andthe width in the left-right direction between the connecting parts 546and 547 is equal to the width of the engagement protrusion 473. Thus,when the separator unit 102 (FIG. 5) is assembled, the flange 53 isfitted to the recess 47, the connecting parts 544 and 545 are fitted tothe engagement recesses 471 and 472, and the connecting parts 546 and547 are fitted to the recesses 47 on the left and right sides of theengagement protrusion 473.

In this fitted state, the right end surface 544 a of the connecting part544 and the left end surface 545 a of the connecting part 545 shown inFIG. 7 are located on the same or approximately the same planes as theright end surface 44 a of the left guide 44 and the left end surface 44b of the right guide 44 of the upstream plate 40 shown in FIG. 6. Thus,as with the end surfaces 44 a and 44 b of the guides 44, the endsurfaces 544 a and 545 a configure support surfaces that support theleft surface 65 and right surface 66 of the fiber member 60. That is,the connecting parts 544 and 545 are located in the same position in theup-down direction as the fourth spacers 424 of the upstream plate 40 andoutside the fourth spacers 424 in the left-right direction, as well asserve as support portions that support the fiber member 60, as with theguides 44.

The upper surfaces 546 a and 547 a of the connecting parts (centralconnecting parts) 546 and 547 shown in FIG. 7 are located on the same orapproximately the same plane as the upper surface 45 a of the guide 45of the upstream plate 40 shown in FIG. 6. Thus, as with the uppersurface 45 a of the guide 45, the upper surfaces 546 a and 547 aconfigure support surfaces that support the lower surface 64 of thefiber member 60.

FIG. 8 is a side view (left side view) of the assembled separator unit102. As shown in FIG. 8, the length L1 from the rear surfaces 55 a ofthe ribs 55 of the downstream plate 50 to the rear surfaces 52 c and 53c of the flanges 52 and 53 is longer than the length L2 from the bottomsurfaces 46 a and 47 a of the recesses 46 and 47 of the upstream plate40 to the front end surfaces of the guides 44. Thus, when the separatorunit 102 is assembled, the rear surfaces 52 c and 53 c of the flanges 52and 53 contact the bottom surfaces 46 a and 47 a of the recesses 46 and47. The length L1 is determined by the length of the connecting parts54, or the like. Also, the length L1 is set such that the length L3 fromthe rear surfaces 55 a of the ribs 55 to the front surfaces 42 a of thespacers 42 is the same or approximately the same as the thickness (thelength in the front-rear direction) of the fiber member 60 with the rearsurfaces 52 c and 53 c in contact with the bottom surfaces 46 a and 47a.

In a side view of the separator unit 102 shown in FIG. 8, the connectingparts 541 and 542 (only 541 is shown) fixed to the left and right lowerends of the flange 52 are extended in the front-rear direction in thesame position in the up-down direction as the second spacers 422. Theconnecting parts 544 and 545 (only 544 is shown) fixed to the left andright upper ends of the flange 53 are extended in the front-reardirection in the same position in the up-down direction as the fourthspacers 424. That is, in a side view of the separator unit 102, theconnecting parts 541 and 542, and 544 and 545 are extended in thefront-rear direction so as to be overlaid on the spacers 422 and 424 andcover the spacers 422 and 424 from outside.

The fiber member 60 is a type of air-permeable porous material and haselasticity (flexibility or contractibility). Specifically, the fibermember 60 is configured as a main component, fiber, including a fibermass consisting of natural fiber, synthetic fiber, or the like, a fiberassembly, such as nonwoven fabric or composition, and the like.

A method for assembling the oil mist separator 101 according to thepresent embodiment will be described. First, the separator unit 102 isassembled. Specifically, the fiber member 60 is fitted to the inside ofthe guides 44 of the left and right spacers 42 protruding from the frontsurface 41 a of the upstream plate 40 shown in FIG. 4B. Thus, the leftand right surfaces 65 and 66 of the upper end, the left and rightsurfaces 65 and 66 of the central portion, and the left and rightsurfaces 65 and 66 of the lower end of the fiber member 60 are supportedby the guides 44 of the first, third, and fifth spacers 421, 423, and425. That is, the left and right surfaces 65 and 66 over the whole inthe length direction (up-down direction) of the fiber member 60 aresupported by the guides 44. Also, the lower surface 64 of the fibermember 60 is brought into contact with the upper surface 45 a of theguide 45, thereby determining the position in the up-down direction ofthe fiber member 60.

Then, the upper and lower flanges 52 and 53 of the downstream plate 50shown in FIG. 4A are fitted to the recesses 46 and 47 around the spacers42 of the upstream plate 40, thereby mounting the downstream plate 50 tothe upstream plate 40. Since the flanges 52 and 53 have approximateU-shapes, the position in the up-down and left-right directions of thedownstream plate 50 with respect to the upstream plate 40 is regulated.Thus, the downstream plate 50 can be easily mounted to the upstreamplate 40 without misalignment.

At this time, the pair of left and right connecting parts 541 and 542supporting the flange 52 by extending the front-rear direction arefitted to the engagement recesses 461 and 462 on the left and rightsides of the second spacers 422. The pair of left and right connectingparts 544 and 545 supporting the flange 53 by extending the front-reardirection are fitted to the engagement recesses 471 and 472 on the leftand right sides of the fourth spacers 424. Thus, the left and rightsurfaces 65 and 66 of the fiber member 60 are supported by the guides44, as well as the end surfaces 541 a, 542 a, 544 a, and 545 a (FIG. 7)of the connecting parts 54. That is, the connecting parts 541, 542, 544,and 545 are members that support the flanges 52 and 53, as well as aremembers that support the fiber member 60, as with the guides 44.

The connecting part 543 supporting the upper end of the flange 52 byextending the front-rear direction is fitted to the engagement recess463 above the through hole 43 of the upstream plate 40. The connectingparts 546 and 547 supporting the lower end of the flange 53 by extendingthe front-rear direction are fitted to the recesses 47 on the left andright sides of the engagement protrusion 473. Thus, the upper and lowersurfaces (upper surface 63, lower surface 64) of the fiber member 60 aresupported by the lower surface 543 a of the connecting part 543 and theupper surfaces 546 a and 547 a of the connecting parts 546 and 547. As aresult, when the downstream plate 50 is mounted to the upstream plate40, the left and right surfaces 65 and 66 and upper and lower surfaces63 and 64 of the fiber member 60 are supported by the guides 44 and 45and the connecting parts 54, and the position in the up-down andleft-right directions of the fiber member 60 is regulated.

With the downstream plate 50 mounted to the upstream plate 40, the fibermember 60 is supported between the front surfaces 42 a of the spacers 42of the upstream plate 40 and the rear surfaces 55 a of the ribs 55 ofthe downstream plate 50. In this case, the protrusions 42 b and 55 bdisposed on the front surfaces 42 a and rear surfaces 55 a press thefront and rear surfaces (front surface 61, rear surface 62) of the fibermember 60. Thus, the positions of the front and rear surfaces 61 and 62of the fiber member 60 are regulated by the protrusions 42 b and 55 b,allowing the fiber member 60 to be held stably.

As shown in FIG. 8, the plate part 41 of the upstream plate 40 and theflanges 52 and 53 of the downstream plate 50 configure a part of theperiphery 102 a of the separator unit 102. The protrusions 48 (FIG. 4B)interposed between the left and right lower ends of the flange 52 andthe left and right upper ends of the flange 53 also configure a part ofthe periphery 102 a of the separator unit 102. Thus, the entireperiphery 102 a of the separator unit 102 has a constant thickness (thelength in the front-rear direction). As a result, the recessed andprotruding shapes allow the flanges 52 and 53 to be easily positioned,as well as increases the rigidity of the periphery 102 a of theassembled separator unit 102.

As shown in FIG. 2, the periphery 102 a of the separator unit 102 thusassembled (temporarily assembled) is fitted to the slit 33 a of thenotch 33 of the upper case 30 from below. Then, the upper surface of theflange 21 of the lower case 20 is fixed to the lower surface of theflange 31 of the upper case 30 by vibration welding. Thus, the assemblyof the oil mist separator 101 is completed.

As shown in FIG. 3, a recessed slit 20 a is provided in a positioncorresponding to the notch 33 of the upper surface of the lower case 20.When the lower case 20 is mounted, the lower end of the separator unit102 is fitted to the slit 20 a. More specifically, as shown in FIGS. 4Aand 4B, flange surfaces 41 d and 53 d are formed over the entire area inthe left-right direction of the lower end of the rear surface 41 b ofthe plate part 41 of the upstream plate 40 and over the entire area inthe left-right direction of the lower end of the front surface of theflange 53 of the downstream plate 50, respectively. The flange surface53 d is formed from the lower end of the flange 53 to the lower surfacesof the connecting parts 546 and 547, and the flange surface 41 d isformed in the same length in the up-down direction as the flange surface53 d. The flange surfaces 41 d and 53 d are fitted to the slit 20 a.

Fitting the separator unit 102 to the slits 33 a and 20 a as describedabove allows the separator unit 102 to be accurately positioned withrespect to the cases 20 and 30 and mounted thereon, as well as allowsthe separator unit 102 to be firmly fixed to the cases 20 and 30. In theassembled oil mist separator 101, the lower end of the downstream plate50, that is, the lower surface of the plate part 51 and the lowersurfaces of the connecting parts 54 (546, 547) is in contact with theupper surface of the lower case 20. Thus, the flow of the blowby gasbelow the downstream plate 50 is suppressed.

Next, there will be described an example of the operation of the oilmist separator 101 according to the present embodiment. As shown in FIG.3, the oil mist-containing blowby gas that has flown into the firstspace SP1 through the through hole 22 passes through the through hole 43of the upstream plate 40 of the separator unit 102 and flows into thefiber member 60 through the rear surface 62 of the fiber member 60. Thisblowby gas flows at increased speed due to narrowing of the flow path bythe through hole 43, passes through the fiber member 60 from the rearsurface 62 to the front surface 61, and flows out of the fiber member 60through the front surface 61, and then hits the plate part 51 of thedownstream plate 50.

At this time, the oil mist contained in the blowby gas is trapped by thefiber of the fiber member 60 by adhering thereto. The trapped oil mistis coarsened into oil masses while moving rearward along the flow of thegas, and the oil masses drop down along the gaps between the ribs 55 ofthe rear surface 51 b of the plate part 51. Or, before reaching the rearsurface 51 b, the oil masses grow into large droplets and drop down. Inthis way, the oil components are separated from the blowby gas. Theseparated oil is guided into the space SP3 of the swelling portion 23 ofthe lower case 20 and then returned to the crank chamber 5 a through thethrough hole 24.

On the other hand, the oil mist-removed blowby gas, which has passedthrough the fiber member 60, mostly flows in the left-right directionthrough the gap between the plate part 51 and the front surface 61 ofthe fiber member 60 and flows into the second space SP2. A part of theoil mist-removed blowby gas flows into the second space SP2 through theleft and right surfaces 65 and 66 of the fiber member 60. As shown inFIG. 8, the connecting parts 541 and 544 on the left and right sides ofthe fiber member 60 are disposed in positions that are overlaid on thespacers 422 and 424. This allows for suppression of an reduction in theflow-path area of the blowby gas flowing out to the left and right sidesof the fiber member 60, allowing for efficient flow of the blowby gas.In this case, the oil separated from the blowby gas drops along the ribs55. Thus, the ribs 55 can suppress the outflow of the oil through theleft and right sides of the rear side of the plate part 51 along theflow of the blowby gas, that is, the ribs 55 can suppress the involutionof the oil. The blowby gas that has flown into the second space SP2flows out through the pipe 34 and is returned to the combustion chambersof the engine 1.

As shown in FIG. 1, during non-turbocharging, fresh air is introducedinto the internal space of the oil mist separator 101R disposed on thehead portion 3R on the rear side of the engine 1 through the passage 12.In this case, the flow in a direction opposite to that described abovegenerates at the separator unit 102. That is, the fresh air flows fromthe second space SP2 to the first space SP1 through the separator unit102. At this time, the connecting parts 54 on the left and right sidesof the fiber member 60, or the like can smoothly guide the fresh air tothe first space SP1 as straightening plates.

The present embodiment can produce the following advantageous effects:

(1) The separator unit 102 is configured to separate the oil mistcontained in the blowby gas generated in the engine 1. Morespecifically, the separator unit 102 includes the upstream plate 40 thatis disposed on the upstream side in the flow direction of the blowby gasand has the through hole 43 through which the blowby gas passes, thedownstream plate 50 that is disposed on the downstream side in the flowdirection of the blowby gas and includes the plate part 51 hit by theblowby gas, and the fiber member 60 that has the rear surface 62 opposedto the upstream plate 40 and the front surface 61 opposed to thedownstream plate 50, is formed in an approximately rectangular shapehaving a predetermined thickness (substantially rectangularparallelepiped shape), and traps the oil mist contained in the blowbygas that has passed through the through hole 43 (FIGS. 4A, 4B). Theupstream plate 40 includes the front surface 41 a of the plate part 41opposed to the rear surface 62 of the fiber member 60, and the pair ofupper and lower recesses 46 and 47 formed in substantially U-shapes andprovided at circumference portions in the upper and lower end sides ofthe front surface 41 a (FIG. 4B). The downstream plate 50 includes thepair of upper and lower flanges 52 and 53 fitted in the recesses 46 and47 (FIG. 4B).

Due to this configuration, it is possible to enhance the rigidity of theseparator unit 102, in particular, the rigidity of the periphery 102 aand to retain the downstream plate 50 in a state of being accuratelypositioned with respect to the upstream plate 40. In other words, theupstream plate 40 and the downstream plate 50 can be easily heldintegral with each other by merely overlaying the flanges 52 and 53 onthe plate part 41.

Accordingly, the upstream plate 40, the downstream plate 50 and thefiber member 60 can be assembled at high positional accuracy, andtherefore, it is possible to sufficiently separate the oil mist.

(2) The downstream plate 50 further includes the rear surface 51 b ofthe plate part 51 facing the front surface 61 of the fiber member 60,and the connecting parts 54 extending along the flow direction(front-rear direction) of the blowby gas that has passed through thethrough hole 43 and having one ends (rear ends) connected to the flanges52 and 53 and the other ends (front ends) connected to the rear surface51 b of the plate part 51 (FIG. 4A). By extending the connecting parts54 in the front-rear direction in this way, the flow direction of theblowby gas is restricted and the flow of the blowby gas in thefront-rear direction after passing the through hole 43 is promoted.Further, positional shift of the fiber member 60 in the width direction(left-right direction) is prevented and separating effect of the oilmist enhances. Furthermore, when fresh air is introduced into the oilmist separator 101 during non-turbocharging, straightening effect isobtained by the connecting parts 54.

(3) The connecting parts 54 include connecting parts 541, 542, 544 and545 that have rear ends connected to both ends in the longitudinaldirection of the flange 52 and 53 extending in the approximate U-shape,i.e., the left and right lower ends of the flange 52 and the left andright upper ends of the flange 53 and front ends connected to the rearsurface 51 b of the plate part 51 (FIG. 7). Therefore, even if theflanges 52 and 53 are provided away from the plate part 51, thedownstream plate 50 can possess the high rigidity.

(4) The upstream plate 40 includes the spacers 42 projected from thefront surface 41 a of the plate part 41 to support the rear surface 62of the fiber member 60 (FIG. 4B). The connecting parts 541, 542, 544 and545 are extended in parallel with projecting direction of the spacer(front-rear direction) so as to overlap with the spacers 42 (422 and424) in a side view of the separator unit 102 (FIG. 8). Therefore, it ispossible to suppress a reduction in the flow-path area of the blowby gasflowing out to the left and right sides of the fiber member 60 due tothe connecting parts 54 and to achieve an efficient flow of the blowbygas. Further, it is possible to suppress a reduction in the flow-pathare when fresh air is introduced into the fiber member 60 from the leftand right sides and to achieve a smooth flow of the fresh air.

The above embodiment can be modified into various forms, andmodifications will be described below. FIG. 9A is a front view of aseparator unit 102A according to a modification of the presentembodiment, and FIG. 9B is a sectional view taken along an axis (lineB-B) in the center in the left-right direction of FIG. 9A. Themodification differs from the above embodiment in the configuration of aplate part 41 of an upstream plate 40. That is, as shown in FIGS. 9A and9B, a protrusion 411 that protrudes rearward from the entire peripheryof a through hole 43 is disposed on the rear surface 41 b of the platepart 41, and the length (thickness) in the front-rear direction of theplate part 41 is increased due to the protrusion 411. In other words,the protrusion 411 configures a thick portion that increases thethickness of the through hole 43 along the flow direction of the blowbygas.

Thus, the length of the through hole 43 in the front-rear direction isincreased, and such a through hole 43 produces favorable blowby-gasstraightening effects. That is, the blowby gas is straightened by thethrough hole 43 lengthened in the front-rear direction and thus flowsforward. Thus, the entire blowby gas that has passed through the throughhole 43 can be caused to flow into the fiber member 60. As a result, theoil mist separation effects can be increased. A thick portion may beconfigured by disposing a protrusion that surrounds the through hole 43,on the front surface 41 a of the plate part 41 rather than on the rearsurface 41 b.

Although, in the above embodiment, the fiber member 60 having the rearsurface 62 (a first surface) facing the upstream plate 40 and the frontsurface 61 (a second surface) facing the downstream plate 50 is disposedbetween the upstream plate 40 and downstream plate 50, a porous memberother than the fiber member 60 may be used. For example, a networkstructure or the like formed from a metal, ceramic, or the like may beused as a porous member.

Although, in the above embodiment, the upstream plate 40 having thefront surface 41 a facing the rear surface 62 of the fiber member 60 (anupstream surface) is disposed on the downstream side of the flowdirection of the blowby gas as an upstream member, the upstream memberneed not be configured as described above. For example, instead ofsingle through hole 43, multiple blowby-gas passage holes may beprovided in the plate part 41 as an opening. Such opening needs not bethe through hole and may be a notch extending from the periphery (theupper end or lower end) of the plate part 41. Although, in the aboveembodiment, the downstream plate 50 having the rear surface 51 b (adownstream surface) of the plate part 51 facing the front surface 61 ofthe fiber member 60 is provide at downstream side than upstream plate 40in the flow direction of the blowby gas as a downstream member, thedownstream member is not limited to the above configuration.

Although, in the above embodiment, the plate parts 41 and 51 and thefiber member 60 are configured to be elongated in the up-down direction,they may be configured to be elongated in the left-right direction orconfigured in a square shape. Therefore, a downstream member may beprovided with a pair of left and right flange parts, instead of a pairof up and down flange parts, and corresponding to such a configuration,a upstream member may be provided with a pair of left and rightrecesses. In the above embodiment, the recesses 46 and 47 of theupstream plate 40 and the flanges 52 and 53 of the downstream plate 50are formed in an approximate U-shape, respectively. However, as long asflange parts are fitted in recesses passing through outsides of a porousmember when assembling a separator unit, the flange parts and recessesare not limited to the above configuration. Although, in the aboveembodiment, the connecting parts 54 are connected to both ends in thelongitudinal direction of the flanges 52 and 53 extending in approximateU-shape, a connecting position of connecting parts are not limited tothe above configuration.

In the above embodiment (FIG. 8), the connecting parts 541, 542, 544 and545 in the left and right outsides of the second spacers 422 and thefourth spacers 424 are configured to cover all of the spacers 422 and424 in a side view. However, as long as the connecting parts areconfigured so as to overlap with the spacers 422 and 424, the connectingparts are limited to the above configurations. The connecting parts 541,542, 544 and 545 may be configured to cover a part of the spacers 422and 424. For example, the length (thickness) of the spacers 422 and 424in the up-down direction may be longer than the length of the connectingparts 541, 542, 544 and 545 in the up-down direction.

Although, in the above embodiment, the separator unit 102 is fitted tothe slits 33 a and 20 a of the upper case 30 and lower case 20, theseparator unit need not be mounted using this method. For example, theseparator unit may be fixed to the cases by welding or the like.Although, in the above embodiment, the oil mist separators 101 includingthe separator units 102 are disposed above the engine 1, they may bedisposed in other positions. Although, in the above embodiment, theseparator unit 102 is applied to the V-type engine of the vehicle havinga turbocharger, it can also be applied to non-V-type-engines and engineshaving no turbocharger in a similar manner.

The above embodiment can be combined as desired with one or more of theabove modifications. The modifications can also be combined with oneanother.

According to the present invention, a downstream member can be assembledwith an upstream member at a high positional accuracy, and therefore, itis possible to sufficiently separate an oil mist contained in a blowbygas.

Above, while the present invention has been described with reference tothe preferred embodiments thereof, it will be understood, by thoseskilled in the art, that various changes and modifications may be madethereto without departing from the scope of the appended claims.

What is claimed is:
 1. An oil separator unit configured to separate anoil mist contained in a blowby gas generated in an internal combustionengine, comprising: an upstream member disposed on an upstream side in aflow direction of the blowby gas and having an opening through which theblowby gas passes; a downstream member disposed on a downstream side inthe flow direction of the blowby gas and having a hit portion hit by theblowby gas; and a porous member including a first surface facing theupstream member and a second surface facing the downstream member andformed in a substantially rectangular shape with a predeterminedthickness so as to trap the oil mist contained in the blowby gas thathas passed through the through hole, wherein the upstream memberincludes an upstream surface facing the first surface, and a pair ofrecesses formed in substantially U-shapes along circumference portionsin both end sides on the upstream surface, and the downstream memberincludes a pair of flange parts formed in substantially U-shapes so asto fit in the pair of recesses.
 2. The oil separator unit according toclaim 1, wherein the downstream member further includes a downstreamsurface facing the second surface, and a connecting part extending alongthe flow direction of the blowby gas that has passed through the openingand having a first end connected to each of the pair of flange parts anda second end connected to the downstream surface.
 3. The oil separatorunit according to claim 1, wherein the downstream member furtherincludes a downstream surface facing the second surface, and a pluralityof connecting parts having first ends connected to both ends in alongitudinal direction of each of the pair of flange parts and secondends connected to the downstream surface.
 4. The oil separator unitaccording to claim 3, wherein the upstream member includes engagementportions formed from side surfaces of the pair of recesses on theupstream surface so that the first ends of the plurality of connectingparts engage with the engagement portions.
 5. The oil separator unitaccording to claim 4, wherein the downstream member further includescentral connecting parts having first ends connected to central portionsin the longitudinal direction of the pair of flange parts and secondends connected to the downstream surface, and the upstream memberfurther includes central engagement portions formed from the sidesurfaces of the pair of recesses on the upstream surface so that thefirst ends of the central connecting parts engage with the centralengagement portions.
 6. The oil separator unit according to claim 5,wherein the porous member includes a pair of first side surfacesextending in parallel with each other and a pair of second side surfacesextending in parallel with each other, between the first surface and thesecond surface, the plurality of connecting parts are extended so as tosupport the pair of first side surfaces, and the central connectingparts are extended so as to support the pair of second side surfaces. 7.The oil separator unit according to claim 2, wherein the upstream memberincludes a spacer projected from the upstream surface to support thefirst surface, and the connecting part is extended in parallel with aprojecting direction of the spacer in an outside of the porous member soas to overlap with the spacer in a side view of the oil separator unit.8. The oil separator unit according to claim 1, wherein the upstreammember includes a thick portion in a periphery of the opening so as toincrease a thickness of the opening along the flow direction of theblowby gas.
 9. The oil separator unit according to claim 1, wherein adepth of each of the pair of recesses equals to a thickness of each ofthe pair of flange parts.